So if an enemy does 1d2 Strength damage through poison and I the DM roll a 2, does that mean that the player has to subtract 2 from their Strength statistic, or do they just take 2 damage, or both? And if the player has to reduce the their Str, when do they get those 2 points back?

Diseases, poisons, spells, and other abilities can all deal damage directly to your ability scores. This damage does not actually reduce an ability, but it does apply a penalty to the skills and statistics that are based on that ability.

For every 2 points of damage you take to a single ability, apply a –1 penalty to skills and statistics listed with the relevant ability. If the amount of ability damage you have taken equals or exceeds your ability score, you immediately fall unconscious until the damage is less than your ability score. The only exception to this is your Constitution score. If the damage to your Constitution is equal to or greater than your Constitution score, you die. Unless otherwise noted, damage to your ability scores is healed at the rate of 1 per day to each ability score that has been damaged. Ability damage can be healed through the use of spells, such as lesser restoration.